How to select a sensor PNP or NPN

Choosing a PNP or NPN Sensor

PNP or NPN Sensor - How to Select

The terms PNP and NPN refer to the type of transistor being used in the sensor. Fortunately, we only need to concern ourselves with how to select a sensor based on the way the sensor will be wired.

Sensors are basically switches that are open or closed based on some condition. This is true for prox switches, photo sensors or any other sensors. Simply put they are all switches that are opened or closed based on whether they detect something or not.

 So why would we select a PNP or NPN?

 PNP (Sourcing)

If we want the switch to supply the + positive side of the power, we will select a PNP Switch. Remember PNP starts with P and it supplies the + Positive side of the circuit.

PNP Photo Sensor Wired

NPN (Sinking)

If we want to supply the -Negative side of the circuit, we will select a NPN switch. Remember NPN starts with N and it supplies the negative side of the circuit.

NPN Photo Sensor Example

How to choose between a PNP or NPN Sensor Click to Download a Printable Version


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